Personality disorder (PD) diagnosis is at a crossroads: There is broad acknowledgment of the significant, negative impact that PD has on individuals and on the course and outcome of comorbid disorders, as well as relatively widespread dissatisfaction with the current categorical system of PD diagnosis. Nonetheless, there also is reluctance to implement an alternative trait dimensional system because: (1) there is no consensus on which set of traits to assess, (2) current trait assessment methods do not reflect either dysfunction or the full range of clinical variability, and (3) the clinical utility of a trait-based system is unknown. The proposed research is significant because it will draw from the full spectrum of the personality trait domain to identify a comprehensive set of specific traits for PD diagnosis, demonstrate how PD characteristics are manifest in both stable and clinical-state-dependent forms, and provide a clinically useful PD diagnostic system that integrates assessment of trait dimensions and psychosocial functioning. The long-term goal of this research is to develop a trait-plus-dysfunction-based clinical assessment system for the reliable and valid diagnosis of personality disorder on which to base the development of effective, more specifically targeted interventions. The specific aims of the current proposal are (1) to establish a set of specific traits that collectively define the trait dimensions of individuals with PD, (2) to establish a set of psychosocial functioning dimensions that collectively define the functional impairment of individuals with PD, and (3) to evaluate prospectively the clinical utility of this two-pronged PD diagnostic system. We plan to do this in three stages: (1) Assessing a large sample on a wide range of measures of both traits and psychosocial function to determine the structure of each domain and ensure that we have identified all components needed to assess personality disorder comprehensively; (2) testing the identified components on another large sample of patients and high-risk individuals, including information provided by family and/or friends, and Axis I symptomatology, and (3) testing the clinical utility of the developed system by assessing a sample of new patients, providing the information to their mental health-care providers, surveying the clinicians for the usefulness and acceptability of the diagnostic system, and examining its predictive validity over 6 months post-intake. We expect that the newly developed system will have high predictive validity and be judged clinically useful; specifically, to be comprehensive and accurate, and useful for communication purposes, for formulating general and specific treatment plans, and for predicting general and specific treatment difficulties. PUBLIC HEALTH RELEVANCE: The current system for diagnosing personality disorder is widely recognized to have problems with both reliability and validity, and to provide little guidance for selecting an appropriate treatment strategy. The goal of this research, therefore, is to provide clinicians and researchers of personality disorder with a revised diagnostic system that is reliable, valid, and clinically useful. It will achieve these goals by identifying and providing the means to assess both the maladaptive trait components of personality disorder in both stable and unstable manifestations, and the ways in which individuals' psychosocial functioning is maladaptive. This will facilitate the development of treatment strategies that target specific maladaptive traits and types of psychosocial dysfunction.